It is known to use a stimulable phosphor sheet to record and visualize an electron optical image obtained in an electron microscope. In particular, such an electron optical image is recorded on the phosphor sheet. Then, the sheet is exposed to stimulating rays such as visible light. This gives rise to generated light emission, which is detected and converted into an electrical signal to make the electron optical image visible.
In order to take sheets of a recording material such as storage-type phosphor sheets out of a housing in an electron microscope and to move them into a position where photographs are taken, a dispenser apparatus shown in FIG. 1 has been heretofore used.
In FIG. 1, sheets 21 of a recording material for use in an electron microscope as described above are stacked on top of each other within a housing 22. The dispenser apparatus comprises a dispenser means 23 for withdrawing and conveying the sheets. The electron microscope includes a microscopic column 24, an observation chamber 25, a fluorescent screen 26, and a camera chamber 27. The sheets on which electron optical images have been recorded are received in a casing 28. The dispenser means 23 has claws 29 (only one is shown). The claws 29 are brought into engagement with the lowermost sheet inside the housing 22, and then the sheet is taken out of the housing. Subsequently, the sheet is sent to a position where a photograph is taken inside the camera chamber 27. An electron optical image is projected onto the sheet 21' placed at this position for photography while using the fluorescent screen 26 as a shutter, i.e., opening and closing it, to photograph the image. Thereafter, the dispenser means 23 carries this sheet 21' into the casing 28, where the sheet is stored.
In the apparatus constructed as described above, the lowermost sheet inside the housing 22 is taken out of it by movement of the claws 29 of the dispenser means 23. This mechanism presents the following problems.
Where the claws 29 are brought into engagement with one edge of the sheet and the sheet is pushed out of the housing, the distance between the front end of each claw 29 and the bottom of the housing 22 must be set less than the thickness of each sheet; otherwise it would be impossible to take out only the lowest sheet. Therefore, it is necessary to set the length of the claws above the base less than the thickness of the used sheets of a recording material. In this case, if the edge portions of the sheets which are to be engaged by the claws warp upwardly, then the claws will fail to engage the edges of the sheets, thus swinging idly. As a result, the sheets may not be moved into the camera chamber.
Where quite thin sheets of a recording material are employed, it is difficult to accurately maintain the distance between the bottom surface of the housing and the front end of each claw. Thus, the claws may swing idly as mentioned above. In addition, the claws may disengage from the edges of the sheets while they are being conveyed, so that the claws swing idly. Two sheets may be transported simultaneously as a stack. In any case, successive conveyance is impeded.